The visually impaired are faced with many challenges when they use mobile devices such as mobile phones. One side of the problem is inputting data without visual aids. As a result of ergonomics and usability design, numerous mobile phone models have clear and well-shaped buttons that can be memorized rather easily. Compared to the input side of the interaction, a bigger challenge lies in getting feedback and information from the device.
Recently, after the computational power of mobile devices has increased, speech synthesizers have become available also for mobile phones. However, due to the ever increasing amount of graphical content on the screen, screen readers are not always able to interpret all information that should be synthesized to speech. In addition, speech output is not a private medium if used without headphones. In certain situations, for example in public spaces, the use of synthesized speech might be uncomfortable to some users.
Most of the visually impaired are accustomed to using their tactile senses for reading Braille and in many cases this might be the preferred way to acquire information. Braille characters are usually represented by six dots arranged in a 2×3 matrix or eight dots arranged in a 2×4 matrix. For representing different letters, numbers or signs, different dots are raised and lowered in the corresponding Braille character. FIG. 1 presents for illustration the raised dots, represented by large disks 101, and lowered dots, represented by small disks 102, of conventional six-dot Braille characters for the letters ‘A’, ‘B’, ‘C’, ‘D’ and ‘E’.
In office or home environments Braille displays are the most common aid used by the visually impaired to read Braille. Braille displays are mechanical devices that are coupled with screen reader software. Textual information which sighted computer users see on the display is transmitted via screen readers to Braille displays consisting of up to 80 Braille cells. Each cell has six or eight dots for representing a respective Braille character, and each of the dots is controlled by an individual electromechanical actuator.
Smaller Braille displays have been developed for mobile use. These displays are typically equipped with 12 to 40 Braille cells and are connected to mobile phones or PDA devices using Bluetooth.
Moreover, instead of placing individual actuators for each dot in the Braille display, devices using a rotating wheel for creating an illusion of actual Braille cells have been built. Users place their finger against the rotating wheel containing Braille characters and thereby receive an impression of a continuous line of Braille characters without actually moving their finger.